This invention relates to brachytherapy, and in particular to a brachytherapy needle assembly, needle stop and template.
Brachytherapy is a procedure for treating cancer by surgically implanting radioactive seeds within target tissue in an affected body part. Brachytherapy treatment can be used in treating prostate cancer, as well as other areas of the body in which radioactive sources can be implanted.
In a brachytherapy treatment for prostate cancer, the seeds are implanted into the prostate at precise locations defined on an x-y plane by pushing the seeds in a z direction through a hollow needle using a stylet inserted in the needle behind the last seed. The seeds are spaced from each other by one or more inert spacers that are implanted together with the seeds. In lieu of spacers, multiple seeds may be provided as a xe2x80x9cstrandxe2x80x9d in which the seeds are connected together by a flexible shroud that is implanted with the seeds. In general, a series of aligned seeds is introduced with each insertion of the needle. The seeds must be accurately placed within the prostate to ensure satisfactory results.
In some brachytherapy devices, seeds are implanted by introducing them into a needle and inserting a stylet in the needle to advance the seeds to the tip of the needle. The needle is then inserted into the target tissue (such as the prostate), and the needle withdrawn while the stylet is held stationary, to unsheath and thereby implant the seeds in the tissue.
In practice, it is difficult to hold the stylet stationary relative to the needle while the needle is being withdrawn to implant the seeds. It is also difficult to determine the starting position for seed delivery (which may be measured relative to the needle tip), and to implant the first seed at that pre-selected position. Even small unintended movements of the stylet relative to the needle, or a slightly inaccurate starting position, can result in inaccurate placement of the seeds, and less effective treatment. Another problem is that the needle frictionally engages the tissue into which it is placed, so that tissue deformation occurs as the needle is withdrawn.
Certain problems associated with the conventional devices used in brachytherapy procedures are overcome by at least some of the instrument embodiments disclosed herein. In particular embodiments, axial movement of the stylet is selectively controlled to diminish inaccurate positioning of the seeds, for example, by selectively fixing axial movement of the stylet relative to the needle or an instrument housing.
According to one disclosed embodiment, the brachytherapy device includes an elongated needle having a sharp end for insertion into target tissue, an elongated stylet which can slide through the needle, and a housing that selectively engages the needle and stylet to selectively fix the needle and stylet against axial movement, while allowing the needle to selectively move axially relative to the stylet when the stylet is fixed against axial movement, and allowing the stylet to selectively move axially relative to the needle when the needle is fixed against axial movement.
In particular embodiments, the housing independently selectively engages the needle and stylet, while in other embodiments the housing disengages the needle while simultaneously engaging the stylet. Certain embodiments of the housing can also selectively engage and disengage the needle in response to relative rotation between the needle and the housing or between the stylet and the housing. Alternatively, relative rotation between the needle and the housing selectively disengages the needle from the housing, and the same relative rotation that disengages the needle also engages the stylet to the housing. Relative rotation refers to movement of the housing relative to the needle or stylet, or rotation of the needle or stylet relative to the housing.
In other examples, the housing, the needle and the stylet are provided with cooperating members that interact to selectively fix the needle and stylet against axial movement. Examples of such cooperating members are a groove and a projection which slides into the groove. For instance, there may be a separate needle groove and stylet groove, with the stylet groove angled to advance the stylet in response to relative rotation between the stylet and the housing. Advancement of the stylet occurs as the projection moves into the angled groove and undergoes both rotation and slight axial displacement. A plurality of different parallel, non-communicating stylet grooves may be provided, so that the stylet can be fixed at a variety of preselected positions along the housing. In contrast, the needle groove can be contained in a plane perpendicular to a direction of axial movement of the needle in the housing, such that rotation of the needle or housing does not axially advance the needle relative to the housing, if such advancement is not desired.
In some embodiments, the projection comprises a projection from the needle that rotates into engagement with a groove (such as a thread in the inner wall of the housing) to selectively fix the needle against axial movement relative to the housing. Alternatively, the groove may be a gap in a stop collar that limits axial movement of the needle relative to the housing, except when the projection from the needle aligns with the gap in the stop collar. When the projection is aligned with the gap, the needle may be withdrawn axially by sliding the projection through the gap.
In yet another disclosed embodiment, the cooperating members that fix axial movement of the stylet and needle are independent triggers carried by each of the stylet and needle. The triggers are independently actuated to move the stylet or needle (or both) relative to the housing. The trigger may be a deformable detent associated with each of the stylet and needle, and the deformable detent is biased to engage the housing. However, the deformable detents of each trigger may be moved out of engagement with the housing to move the stylet or needle to which the trigger is attached. In particular examples, the housing includes a longitudinal slot having teeth along both longitudinal edges of the slot. Both of the separate triggers project out of the housing through the slot, and are biased into engagement with the teeth along the slot. However, the triggers can be moved away from the teeth to free the trigger for longitudinal movement in the slot. Movement of each trigger also moves the associated needle or stylet axially in the housing.
The instrument may be provided with a spacer extending from a distal end of the instrument, and a length of the spacer may be selectively altered to set a spacing distance between a distal tip of the instrument and a stop surface against which the spacer rests. A stop member can also be provided that opposes advancement of the needle along the path of insertion beyond a preselected distance. For example, the stop member can have an aperture or notch sufficiently large to permit the needle to pass through, but which is sufficiently small to prevent an enlarged diameter portion of the instrument to pass through. This arrangement prevents advancement of the needle beyond a preselected distance. The needle can be provided with a mating member that mates with the stop to resist rotation or axial movement of the needle. For example, the mating member can be engaged by rotating the needle to move a projection from the needle into a receptacle (such as an arcuate notch) on the stop member. In a particular embodiment, the stop member is a stop plate which includes a series of slots with notches at pre-selected positions in which the needle can seat.
The stop member may interfere with a clear view of a target area into which the needle is to be inserted. It is therefore sometimes advantageous for the stop member to be movable so that it can be selectively aligned with the path of insertion, or moved out of the path of insertion to provide a more unobstructed view when the guide function of the stop member is not required. The stop member can be made pivotable to facilitate movement of the stop member in and out of the field of view along the path of insertion of the needle. For example, in some embodiments the stop member is a pivotable arm having a plurality of notches that are selectively alignable with a template position through which the needle is to be inserted. When the pivotable arm pivots in a plane substantially perpendicular to the path of insertion and parallel to the plane of the template, the notches can be selectively aligned with almost any x-y position in the template by selecting a particular notch with the arm at a particular pivot angle.
In yet other described embodiments, the stop member includes a proximal stop member and distal stop member, such as a pair of parallel stop plates, that are movable apart from one another along the path of insertion of the needle to a limit distance. The proximal and distal stop plates have aligned apertures or notches through which the needle may be inserted, and the apertures or notches of the distal stop plate are smaller than the apertures of the proximal stop plate, so that advancement of the needle along the path of insertion moves the distal stop plate away from the proximal stop plate. However, the apertures or notches of the distal stop plate are deformable to allow the needle to be inserted through the distal stop plate by the application of sufficient insertion force after the distal stop plate reaches the limit distance. The non-deformed apertures or notches in the distal stop plate appear as a partial occlusion of the corresponding aperture or notch in the proximal stop plate. Deformation of the aperture or notch in the distal stop member provides a visible cue that the aperture or notch has already been used, because its enlargement will be visible through the corresponding notch in the proximal stop plate.
In yet other embodiments, the brachytherapy device has a housing that selectively engages the needle and stylet to selectively fix the needle and stylet against axial movement, wherein relative rotation between the housing and needle selectively engages the needle to the housing to fix the needle against axial movement relative to the housing, and relative rotation between the housing and the stylet selectively engages the stylet to the housing to fix the stylet against axial movement relative to the housing. Likewise, relative rotation between the housing and the needle selectively disengages the needle from the housing to permit axial movement of the needle relative to the housing, and relative rotation between the housing and the stylet selectively disengages the stylet from the housing to permit axial movement of the stylet relative to the housing. In particular embodiments, the same relative rotation between the housing and the needle that selectively engages the needle to the housing also disengages the stylet from the housing.
In those embodiments in which rotation of the needle relative to the housing is used to selectively engage or disengage the needle from the housing, rotation of the needle reduces frictional engagement between the needle and the target tissue. This reduction in frictional engagement permits the needle to be withdrawn from target tissue (such as an organ) more easily, without deforming the target tissue. Adherence of the needle to, for example, prostate tissue as the needle is withdrawn can deform the prostate, and interfere with the precise placement of radioactive seeds for the treatment of tumor loci.
Recitation of any aspect of a device in this Summary of the Disclosure is not intended to imply that the aspect is an essential element. This Summary is instead provided to facilitate understanding of the following detailed description.